1. Field of the Invention
The present invention relates to a piezoelectric transformer, a driver circuit incorporating the piezoelectric transformer, and a liquid crystal display apparatus incorporating the driver circuit.
2. Description of the Related Art
A conventional type of liquid crystal color display apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 11-174976. The liquid crystal color display apparatus disclosed therein requires three inverters corresponding to the three primary colors, so that a backlight provided in the liquid crystal color display is allowed to emit red (R), green (G), and blue (B) light components. Thus, the liquid crystal color display apparatus also includes three transformers respectively corresponding to the three inverters. As a result, the liquid crystal color display apparatus suffers from the problems of increased size and high cost.
In order to overcome the problems described above, preferred embodiments of the present invention provide a piezoelectric transformer, a driver circuit incorporating the piezoelectric transformer, and a liquid crystal display apparatus incorporating the driver circuit, which has a much smaller size and much lower cost than conventional devices.
According to first preferred embodiment of the present invention, a piezoelectric transformer including a piezoelectric unit is provided. The piezoelectric unit includes a plurality of driver units divided by at least one groove extending in the longitudinal direction of the piezoelectric unit from one end thereof, and also includes a plurality of generator units, opposing the plurality of driver units, divided by at least one groove extending in the longitudinal direction of the piezoelectric unit from the other end thereof. Opposing pairs of the driver units and the generator units constitute a plurality of transformer units. The transformer units differ in length from one another. Thus, the transformer units each have different resonant frequencies.
According to another preferred embodiment of the present invention, a driver circuit for driving a plurality of light sources includes a piezoelectric transformer according to the preferred embodiment described above, in which the plurality of transformer units correspond to the plurality of light sources. The driver circuit also includes a high-frequency generator for applying to the piezoelectric transformer a plurality of drive voltages each having a frequency that is substantially equal to the natural longitudinal resonant frequency of one of the transformer units. Thus, each of the light sources emits light only when the associated transformer unit is resonating.
According to another preferred embodiment of the present invention, a liquid crystal display apparatus includes the driver circuit according to the preferred embodiment defined above, and the plurality of light sources driven by the driver circuit. The liquid crystal display apparatus has a much smaller size and lower cost than conventional devices.
In accordance with various preferred embodiments of the present invention, a plurality of transformer units which differ in length from each other and which each have different resonant frequencies are provided in a single piezoelectric unit, which allows the transformer to have a much smaller size and much lower cost. The transformer incorporating the piezoelectric unit may be used to replace a plurality of transformers. Accordingly, by incorporating the transformer, a driver circuit has a much smaller size and much lower cost. Furthermore, by incorporating the driver circuit, a liquid crystal display apparatus is produced to have a much smaller size and much lower cost.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.